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METEOROLOGICAL FACTORS RESPONSIBLE FOR HIGH CO (CARBON MONOXIDE) LEVELS IN ALASKAN CITIES
Bowling, S. METEOROLOGICAL FACTORS RESPONSIBLE FOR HIGH CO (CARBON MONOXIDE) LEVELS IN ALASKAN CITIES. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/3-84/096.
High winter carbon monoxide levels in Anchorage, as in Fairbanks, are due to intense nocturnal (ground-based) inversions persisting through the periods of maximum emissions and at times throughout the day. The problem is exacerbated by the large amounts of carbon monoxide emitted during cold starts at low temperatures. The Anchorage situation is unusual in that the nocturnal inversion develops most often with a substantial north-south pressure gradient and easterly geostrophic winds. The Chugach Range to the east sometimes produces a 'wind shadow' effect in the city, and almost all the CO violations examined occured in these conditions. There is evidence that inversions are significantly stronger, and dispersion conditions probably worse, near the mountain front than at the airport weather observation station. CO forecasting in Anchorage would require close cooperation between the U.S. NOAA Weather Service and the Municipality; improvement in communications between the Fairbanks North Star Borough and the Weather Service is also essential if the quality of the Fairbanks CO forecasts is to be improved. Measurements of mixing heights in Fairbanks suggest that a mixing height of 10 m be considered the maximum for worst-case modeling of surface-source pollutants; values as low as 6 m were observed. As an interim measure, similar values are recommended for Anchorage.